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Aluminum Head? or Original?

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Go_Dogs_Go

Go_Dogs_Go

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I am going to rebuild the wife's Sprite 1275 engine. My overall goal is to have a bored engine (.020 or .030), new pistons, a slightly better street cam, headers, and new rockers. I have "new" condition SU2s so I don't want to toss them, but maybe replace the intake manifold for them. Without replacing the carbs (this year) I realize that i am limiting some of the improvement to performance, but I accept that. Better performance, longer life, but not a race engine is what I am shooting for.

Moss and other catalogs claim greater flow from the aluminum heads using stock sized valves. For less money I can get slightly modified cast heads having slightly larger valves and "pocket ported". What is the opinion here for either option?

Also would roller rockers add anything to the performance? I think they are great to look at, but is it worth the money? Right now I have the old pressed style rocker. Opinions on replacing the rockers with brushed units or ?

What are your experiences and opinions on these top-end topics so far?
Thank you!
 
Go for the ported iron head. Rockers of different ratio may of may not make a difference depending on your cam.
 
I would strongly recommend you contact Hap at Acme Speed Shop and speak with him. He can steer you in the right direction and won't have you spending money you don't need to.
 
The Pierce alloy, 5 port heads do not flow as well as a good hand ported iron head, but since they run cooler a higher compression ratio can be used. According to my engine builder, APT, the ports on the alloy head are too big for anything but forced induction where the slower velocity is not an issue. BTW, those SU's are not the drawback you think: HP is not much different than with Weber's and drivability is often better.
 
I would stay with the SU's.
Also, if a street engine, be careful with cam selection. The OEM engineers were not stupid (mostly). Most enthusiasts put in a cam that helps horsepower at high RPM, which most street engines rarely see, and this comes at the expense of low end torque which is a far more important parameter for a street car. Thus, they end up significantly worse off for their trouble.

Fred
 
kalist said:
I would strongly recommend you contact Hap at Acme Speed Shop and speak with him. He can steer you in the right direction and won't have you spending money you don't need to.
Click to expand...

The boy can do some beautiful porting.
He's ported me an intake recently. Trick stuff.
His ported heads are works of art.
:thumbsup:
 
What head did you use for porting Gundy?
 
Jack, Hap used the stock head from my 1974 1275 (smog head, just plugged the ports) when he did the port/polish work for the Tunebug's engine.
 
After digging a bit I never found flow data for the aluminum heads so I just gave up. Hard top make a decision without any comparative data.
 
Go dogs, I build this thing for a living, for race and steet, so I worked with about everyhting out there ever offered for them, here's my take on this stuff.

The aluminum aftermarket heads are not the best castings in the world, they flow no where near as good as stock head, so they need porting to improve and even then vs a ported cast head are still inferior. In theory a aluminum heads do sound like a good deal, it's just the one for our cars leave alot to be desired. Besides that but cast iron 1275 head are near bullit proof, with the exception of the Cooper S head, and it proned to crack between the intake and exahaust seat, but a good Midget 12G940 (pre smog) or the 12G1316 (smog head) are both fine cylinder heads.

Most of the aftermarket intakes are not worht the trouble, the most common one the Mainfolw is nothing more than stell pipe, and it not a great flower, the 1275 intake is good intake and the earlier 1275 intake with the small round holes leading into the balnce tube is the best one.

As for roller rocker arms, they produce less friction across the valve tip, but that not huge issue on a street engine and not reason enough to buy them, increased ratio would be the main reason to buy them and even then you can just get the higher valve lift camshaft you want without the roller roacker arms, if you go for roller roacker arms on a 1275, there is really only one good choice, the Titan 1.5 set up, stay far away from Harland Sharp 1.3 set up, you can also get offset bushing foe the stock roacker arms to increase the ratio on them.

Here's the three biggies to getting the most bang for the buck out of a 1275 street perforamcne engine.

Higher compression ratio and most of that can be done with a taller compression height pistons that specs at 8.8 to 1 or 9.7 to 1, siamese port cylinder heads love compression ratio, so around 10.0 to 1 on a 1275 wakes it up.

A good camshaft, I use APT cams and lifter in my engine and rebuild engine kits.

Head porting

Oh and in that order, if you put a ported head on otherwise stock engine you will notice very little difference, the ported head needs the cam and extra CR to do it's job properly.

I do al the above work and do engine kit or build it for you, give me a shout if I can help, several of these guys has used my engines, so hopefully that bodes well for me :smile:
 
jlaird said:
What head did you use for porting Gundy?
Click to expand...

It's one of those GT7 Longman heads. Cast iron.
I understand they have a weak area between valves
and to watch out about running hot and cracking that sucker.
Mimi runs cool as a cucumber so far...about 3000 miles
on the engine. Mostly by old lead foot me.
So far so good.
:devilgrin:
 
Great input from everyone!
Hap, I already sent you email today and you responded. I like what you are suggesting.

What is the advantage to higher ratio rockers? And what is the upside/downside to getting that higher lift from the cam shaft instead of the rockers?

I see "wedged" cranks for sale. What are they? I think it is probably out of my application but I am curious.

Yep, TulsaFred, nice reminder of the cam. I am not freeway driving this car.

Again, this is terrific help to me and I appreciate the time it takes to help.
GDG
 
58Custom said:
After digging a bit I never found flow data for the aluminum heads so I just gave up. Hard top make a decision without any comparative data.
Click to expand...

I thought the Classic Motorsport people did a comparison a few years back? The same folks who found there to be very little difference between the SU's and the Weber on the street.
 
Go_Dogs_Go said:
Great input from everyone!
Hap, I already sent you email today and you responded. I like what you are suggesting.

What is the advantage to higher ratio rockers? And what is the upside/downside to getting that higher lift from the cam shaft instead of the rockers?

I see "wedged" cranks for sale. What are they? I think it is probably out of my application but I am curious.

Yep, TulsaFred, nice reminder of the cam. I am not freeway driving this car.

Again, this is terrific help to me and I appreciate the time it takes to help.
GDG
Click to expand...

Higher ration rocker open the valve further, so produce more vale lift, but you can do the same thing with a higher lifter cam. I tell people roller rocker are just a part you bolt on, ther are commitment, you need to shom them at the pedestals, you need to make or buy solid spacer for them, and they take atleast 2-3 trial fits to get the clearence good on them, then sometimes you may need a longer pushord and if you do, that means a 5/16 tubular push rod, and to be honest with you, you really need to modify the block for that, or otherwise they rub in the bottom of the lifter bore on the 1275s. Unless you're just trying to make the world's trickest A series engine and money is no object, stay away from roller rocker ams, I charged $300 in a build just to set them up, and it takes all day long, most of the time to do it. Oh and run from the Harland Sharp 1.3 roller roacker arms you see on ebay, most people who have bought them, have never fiquired out how to install them and you have to modify the push rod holes in the head for clearence with those things, those thing are really a bad idea, for hardly no improvoment, other than bragging to your buddys you have roller rocker arms :smile: Another lesson learned from experience :smile:

Myself and David Anton (APT) are a couple of the only folks in the country that wedge lighten MG crankshafts, and it is really something for a racer whio is looking for that last adavantage, ligther rotating mass does not give you any additional HP, it just gets you to what you have quicker, it would be a waste of money in a street engine, go for a aluminum flywheel before you do a wedge crank, the aluminum flywheel results in a greater loss of rotating mass for less money, now mind you this advice is comng from the guy who does this job more than anyone else in the US, probably the world.

I guess I'm the only guy in the US that lightens the rare EN40B crank, it's not that I'm the only one who has ever done it, I just the only one crazy enough to do it twice :smile: They are really hard steel and eat up really expensive end mills, so it cost alot more than doing the normal EN16T 1275 crank.
 
Hap, I ended up talking to some people about heads when I was up North. I asked a lot of questions about a pierce cross flow head. Turns out he was the brother of the pierce who does all that. Does the crossflow itself give you anything extra?
That head was a lot lower than a stock 1275 as well. Before I would spend the kind of money for an aluminum head, I would want to see a car with somebody putting it through its paces for a while. I wonder if they ever have problems with warp-age on those. You also want the motor to last.
 
Westfield_XI said:
The Pierce alloy, 5 port heads do not flow as well as a good hand ported iron head, but since they run cooler a higher compression ratio can be used. According to my engine builder, APT, the ports on the alloy head are too big for anything but forced induction where the slower velocity is not an issue. BTW, those SU's are not the drawback you think: HP is not much different than with Weber's and drivability is often better.
Click to expand...

I've had excellent results from David's heads also.

Quite a few to choose from too.

https://aptfast.com/ListItems/MainCategory/Cylinder Head, Head Components.aspx

https://dl.dropbox.com/u/19278540/pdf%20files/Alloy1275V12G1316_flow.pdf
 
regularman said:
Hap, I ended up talking to some people about heads when I was up North. I asked a lot of questions about a pierce cross flow head. Turns out he was the brother of the pierce who does all that. Does the crossflow itself give you anything extra?
That head was a lot lower than a stock 1275 as well. Before I would spend the kind of money for an aluminum head, I would want to see a car with somebody putting it through its paces for a while. I wonder if they ever have problems with warp-age on those. You also want the motor to last.
Click to expand...

Kim, the biggest thing the cross flow head does is give each cylinder it's own intake port vs siamesed intake ports, so yes that would be a improvment, it of course move the carbs to the distributor side of the motor, and on the MGB, and I'm sure the Midget as well makes stuff like getting to your distributor, oil filter, starter, hard to reach for that reason, I'm not a big fan of crossflow heads, I don't like anything that make the car harder to work on. The casting in the aftermarket heads as I mnetioned is rough, so it needs work to be a improvment. Then there the issue of now you got this big port x-flow head and whatcha gonna run for carbs, 1-2 webers (2 would be too much fuel reequirement, in otherwise more for show than anyhting else), twin HS4s are too much for a street A series, I guess the hot set for the x flow head in my mind would be a single DCOE, and good intake, it would also take up the less space for getting to dizzy and oil filter a little easier maybe.

Bottom line, it's alot of money, buy the head for what $1000, then get someone to port it for another $600-700, then buy the weber DCOE and intake, I'm guessing thats another easy $1000, and now get you trick aluminum valve cover, now you're looking at near $3000 for the top end and you know most guys going this far, would throw another $500 at it for the Titan 1.5 roller rocker set up.

And the answer is yep for $3500 it would be a nice inprovment :smile:

Here's my take on all this as for A series street power

9.0 to 1, good cam, everyhting built right aprox. 70 hp

10.0 to 1 good cam, everything right aprox. 80 hp
(that bacily is my stage I motor)

Add a ported head to above recipe aprox. 90 hp
(bascily my stage II engine)

Make it 1380 cc big bore, closer to 100 hp

Throw everything possibly on earth at it, xflow heads, weber, higher ratio roller rocker arms, barely streetable cam, still normal asperation ,maybe 110 hp, and this combo in a xflow or normal parted head with the racier cam would be the least favortite to drive at any other than full tilt, real fuzzy in normal traffic situactions.

If I personally had a Spridget 1275 street car, I'd probably lean more along the lines of a stage II motor, that would give me a nice bang for the buck, and 90% of the HP of the more expensive choices.
 
That makes sense Hap. I never thought about how hard it would be to work on with the carbs on that side. Sounds like you go it figured out. I have had a couple engines with a racing type cam and it makes driving in traffic really impractical.
One was a 2000 Ford Pinto and it never idled right with that cam and snapped timing belts on occasion to the point I just left the cover off of it and carried a spare belt in the trunk and could change one roadside. I remember you telling me how much time and trouble it was doing the ports on those heads, but that sounds like the way to go.
 
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